Satellite systems have been used extensively to provide a variety of satellite-based services and functions. For example, current satellite systems provide communications services, broadcast and multicast services, earth imaging, radar, weather monitoring, astronomical observations and the like.
A satellite system may include a single satellite or a plurality of satellites whose functionality are combined in some manner. Satellites may travel in geosynchronous orbits (GSO) or non-geosynchronous orbits (NGSO), and may be referred to as GSO satellites or NGSO satellites, respectively. A satellite of a single satellite system typically is a GSO satellite, so that the satellite may provide continuous service over a distinct coverage area on the surface of the earth. Pluralities of satellites may include GSO and/or NGSO satellites.
A GSO satellite orbits the earth approximately once per day in synchronous motion with the revolution or rotation of the earth. The GSO satellite may be positioned at some inclination with respect to the earth's equator—“geostationary” referring to the special case in which the orbit of a GSO satellite is positioned in the equatorial plane (at an inclination of zero degrees). Communicating with a geostationary satellite has some obvious advantages in that an earth station antenna can remain pointed in one stationary and fixed direction without the need for active control to maintain pointing at the geostationary satellite.
Interference mitigation in many satellite systems often involves geolocating source(s) of interference (sometimes referred to as interference sources, interferers or the like) on or near the surface of the earth. Many techniques have been developed for this geolocation, including frequency difference of arrival (FDOA) techniques that rely on a Doppler shift in interfering signals between an interferer and satellite, and time difference of arrival (TDOA) techniques that rely on interfering signals received by multiple satellites. But for interference received by GSO satellites, FDOA information may be difficult to detect due to a weak Doppler signature received by such satellites; and for TDOA, multiple GSO satellites may not be in a close enough vicinity of one another to render the TDOA approach effective.